Study of... without knowing what the scientists are studying, you cannot know exactly what instruments they are using.
Microscopes... But only for the really small stars.
ammeter
They use their eyes and also a variety of instruments, based on the ground or in space, which are sensitive to a large range of electromagnetic radiations.
Thetools scientist use are Barometers, Anemometer's thermometers Richter Scale
The insrument that is used for scientist to study earthquakes is a seismogram
There are a number of ground instruments and satellites used to study the sun. To study the interior of the sun, scientists study sound waves vibrating inside of it. The photosphere, chromosphere, and corona, are all observed using special telescopes to detect the corresponding rays coming from each section.
whattools do scientist use to study meteors
Telescopes
Tools That Volcanologist Use Are...Seismographs,Seismometers,. Some Instruments Are Also...EDM,Leveling,GPS,Tilt. And Some Instruments That Can Determine How Much Lava Is Moving Underground Like VLF,Em3-1
Binoculars
Telescope
There are a number of instruments that might be used to study such a phase transition, depending on precisely what it is you're trying to measure. A couple of guesses: thermometer, calorimeter.